Foreign aid doesn't seem to be very growth promoting. Free trade is certainly something I would advocate for poor countries. Health was a very important predictor of economic growth, and it's especially a problem in some sub-Saharan African countries. There are some good ideas about how you could specifically direct investment in the health area.
Russ Roberts interviews Robert Barro, Harvard University Professor and Hoover Institution Senior Fellow, on the economics of growth, what the developed world can do to help poor people around the world, and the role of US assets and the dollar in world finance.